1. Field of the Invention
The present invention relates to an optical disc drive system capable of processing both an optical disc having a data protection function for preventing data from miss-erasure and alteration and an optical disc without such a data protection function.
2. Description of the Related Art
An example of a conventional optical disc drive system will be described with reference to FIGS. 3 and 5. FIG. 3 is a block diagram showing an example of a conventional optical disc drive system. Light emitted from a laser 25 (about 660 nm in wavelength for DVD-RAM) constituting a portion of an optical head 2 passes through a collimator lens 24 to be collimated to parallel light beams 22. A light beam 22 is focused upon an optical disk 11 via an objective lens 23 to form a spot 21. The reflected light beam 22 is sent to a servo detector 26 and a signal detector 27 via a beam splitter 28 and a hologram device 29. Signals detected with the detectors are added or subtracted to form servo signals such as a tracking error signal and a focus error signal which are input to a servo circuit. In accordance with the input tracking error signal and focus error signal, the servo circuit controls the positions of the objective lens 31 and optical head 2 to set the optical spot 21 to a target read/write area. An addition signal of signals output from the detector 27 is input to a signal reproduction block 41. The input signal is subjected to filtering and equalizing by a signal processing circuit to be digitized thereafter. This digital signal is processed by an address detector and a demodulator. In accordance with the address signal detected by the address detector, a microprocessor calculates the position of the optical spot 21 on the optical disc 11 and controls an automatic positioning means to move the optical head 2 and optical spot 21 to the target read/write unit area (sector).
If a command from a host to the microprocessor is a write command, the microprocessor receives write data from the host and stores it in a memory, and controls the automatic positioning means to move the optical spot 21 to the target write area. After the microprocessor confirms from the address signal supplied from the signal reproduction block 41 that the optical spot is correctly positioned at the data write area, the microprocessor controls a laser driver and the like to write the data stored beforehand in the memory into the target write area.
As shown in FIG. 6, address data is written in each read/write unit area at the start field thereof. By detecting this address data as the address signal, it is possible to check the position of an optical spot immediately before the data is written.
FIG. 5 is a flow chart illustrating the operation of the optical disc drive system, by taking as an example an optical disc drive system for driving a rewritable type DVD-RAM stipulated by International Standards ISO/IEC-16824.
As a disc is loaded or a power of the optical disc drive system is turned on, the optical disc drive system first executes a process of identifying the type of the medium. This system generally has a read function not only for DVD-RAM media but also for read-only type media such as CD-ROM and DVD-ROM. Therefore, the optical disc drive system first executes the identification process to identify the type of the loaded medium. The identification process changes with each system. For example, one system identifies the medium type from a reflectivity and the analog characteristics of the reproduced signal such as a focus error signal, whereas another system identifies the medium type from the contents (data) read from a disc physical information area in a disk substrate.
If the medium type is identified as a rewritable type, i.e., DVD-RAM, the optical disc drive system reads data recorded in a defect management area to check whether the optical disc is already formatted. If unformatted, it stands by until a format command is supplied from the host or user.
If formatted, the optical disc drive system executes a read/write preparation process such as a calibration process and a logical consistency check process, and thereafter waits for a command from the host or user. Upon reception of any command, the optical disc drive system checks the type of the command. If it is a write command, a write process is executed, whereas if it is a read command, a format command or an eject command, then a corresponding process is executed. These processes are usually terminated normally. However, if the write operation were failed from unexpected reasons, an error process such as a retry process and a replacement process is executed.
Generally, in the case of DVD-RAM, after the write process, the written data is read to verify whether the data was correctly written, and if necessary the replacement process using other read/write unit areas is executed. In this manner, the reliability of written data is improved. Management information on reassignment of read/write unit areas is recorded in a specific area (defect management area) of the disc.
DVD-RAM is used with such a highly reliable optical disc drive system, and data written can be basically rewritten freely. There is, therefore, a possibility that important written data is erased or altered because of miss-operation by a user or a failure by the host.
As one protective method, a so-called xe2x80x9cwrite-protect functionxe2x80x9d is known. However, this write-protect functionxe2x80x9d can be released by a user freely. It is therefore impossible to prevent data from being destroyed by a miss-operation of a user.
An example of a magneto optical disc used for solving the above problem will be described. A magneto optical disc is a rewritable type storage medium which can erase or rewrite user data in a user data area. There are needs for using a magneto optical disc as a write-once type storage medium which cannot erase or write user data.
According to CCW System (or MO-WORM System) stipulated in ISO-IEC 11560, media type identification data representative of an magneto optical disc type is recorded in a control data area outside of a user data area. Whether a magneto optical disk is a rewritable type or a write-once type is determined from this media type identification data.
As a write-once type magneto optical disk is loaded, the magneto optical disc drive system inhibits an erase operation and a rewrite operation of the user data area with user data already written. Namely, this system has a data protection function for preventing erase and overwrite of a magneto optical disc which is originally of a rewritable type. The same magneto optical disc drive system can access both the write-once magneto optical disk with the data protection function and the rewritable type magneto optical disc. Application field of the magneto optical disc can be broadened and the media cost can be reduced.
However, if a similar method is applied to the optical disc drive system stipulated only with the rewritable type specifications, such as DVD-RAM, there arise the following problems.
The specifications for rewritable type discs exist already and are prevailing in markets. Optical disc drive systems for driving such optical discs in conformity with those specifications also exist already. Under such environments, even if media type identification data is newly registered in a media type identification area similar to magneto optical discs, the already existing systems cannot be altered and cannot drive optical discs with the data protection function.
Not all optical disc drive systems use the media type identification data for identifying the medium type. Even if new code data still not defined is recorded as the media type identification data, a conventional optical disc drive system cannot recognize the meaning of the code data and the operation becomes undifined.
DVD-ROM is a read-only medium. It generally requires a cost of hundreds of thousands Yen and takes a time of one day or longer to write data in a single DVD-ROM. Therefore, thousands or more of DVD-ROMs are generally formed at a time. DVD-ROMs are used only in the field of mass production.
As described above, even if a data protection function is introduced to an already existing optical disc drive system, an already existing optical disc drive system without the data protection function may destroy data on an optical disc with the data protection function.
It is an object of the present invention to provide an optical disc drive system capable of realizing a data protection function by changing almost no hardware and physical specifications, and eliminating a possibility that a conventional system not recognizing this expanded function may erase or alter data.
In order to achieve the above object of the invention, the following approaches are incorporated.
(1) An optical disc drive system is provided which can process both a rewritable optical disc and an optical disc with a data protection function limiting data rewrite and data addition. These discs each have a plurality of divided data recording unit areas and have address data of the data recording unit areas in the form of read-only data. Address data of the optical disc with the data protection function is set differently from address data of the rewritable optical disc. The address data of each data recording unit area of the optical disc with the data protection function is related to the address data of the same data recording unit area of the rewritable optical disc through arithmetic or logical addition of a constant.
Even if an optical disc with the data protection function is driven with a conventional optical disc drive system which cannot recognize the data protection function, the conventional optical disc drive system cannot access the target data write area because the target address does not exist at the position expected by the conventional optical disc drive system. There is therefore no risk that the conventional optical disc drive system without the data protection function may erroneously destroy data through erase or overwrite. A high reliability of the data protection function can therefore be improved. The address data of each data recording unit area of the optical disc with the data protection function is related to the address data of the same data recording unit area of the rewritable optical disc through simple arithmetic or logical addition of a constant. Therefore, it is easy to develop a modification or alteration method from a conventional optical disc drive system to an optical disc drive system with the data protection function. A high reliability optical disc drive system with the data protection function can therefore be supplied with low cost. The main different point between the optical disc drive system with the data protection function of this invention and a conventional optical disc drive system is only address data. It is easy to support the addition of a read/write function for a conventional optical disc drive system without the data protection function to the optical disc drive system with the data protection function of this invention.
(2) In addition to the above, address data of an optical disc with the data protection function is set so as not to exist in the rewritable optical disc.
Even if an optical disc with the data protection function is driven with a conventional optical disc drive system which cannot recognize the data protection function, the conventional optical disc drive system cannot access the target data write area because the target address does not exist at the position expected by the conventional optical disc drive system. There is therefore no risk that the conventional optical disc drive system without the data protection function may erroneously destroy data through erase or overwrite. A high reliability of the data protection function can therefore be improved. Similarly, it becomes easy to add the read/write function of a conventional optical disc drive system and lower the cost. Further, the address data of a conventional optical disc is not overlapped with and is perfectly different from the address data of the optical disc with the data protection function. By utilizing this point, the conventional optical disc and the optical disc with the data protection function can be easily discriminated.
(3) Information for discriminating the optical disc with the data protection function from the rewritable optical disc is recorded in the identification data area outside of a normal user area.
By reading this identification data, the optical disc drive system with the data protection function of this invention can easily discriminate between a conventional optical disc and an optical disc with the data protection function of this invention.
(4) An overwrite protection function is provided which in response to a user data write command from a user or a host after an optical disc with the data protection function is loaded, a read operation for reading the data recording unit area is first executed when user data is to be written in the data recording unit area of the optical disc with the data protection function, a data write operation is inhibited if user data is already written in the data recording unit area, the user data is written in the data recording unit area if user data is not written in the data recording unit area.
Even if there occurs a miss-operation of a user, a defective host or a defective host program, already written data will not be lost so that data archiving is possible with very high reliability. Even if a malicious user intends to alter data, the optical disc drive system of this invention does not allow data overwrite and erase so that record data can be stored with high security.
(5) In the optical disc drive system of this invention, finalization data is written in the optical disc with the data protection function upon reception of a command from a user or a host, a presence/absence of the finalization data is confirmed when an optical disk is loaded, and if there is the finalization data, neither a write-once operation nor a rewrite operation is executed related to the loaded optical disc.
By applying the finalization process to an optical disc with already written data, already written data will not be lost and nor data addition is possible. Even if a file system is used which can apparently rewrite data by using a data addition type medium such as CD-R, the already written data cannot be changed physically and logically. Therefore, already written data will not be falsified or altered. Neither a write operation nor a write-once operation is possible for an optical disc with the data protection function after the finalization process is executed. This optical disc is therefore equivalent to a read-only medium so that it is applicable to a medium used for data distribution purposes or the like. The application field can therefore be broadened.
(6) When a format command is received from a user or a host after the optical disc with the data protection function is loaded, a format operation is not executed until it is confirmed that the optical disc with the data protection function is unformatted.
There is no possibility that data already written in the optical disc may be erased by the optical disc drive system of this invention even if various means are used. Reliability of already written data can be improved considerably.
(7) The optical disc with the data protection function has an error correction block having a size of a plurality of sectors, and a write command from a user or a host is not executed if the write command contains a size smaller than the size of the error correction block.
A conventional optical disc drive system receives a data write command containing a unit (sector) smaller than the unit (error correction block) of error correction for data written in an optical disc. Therefore, a read-modify-write process is necessary wherein before data is written in a single sector, data in nearby sectors is first read and thereafter a portion of the read data is replaced by written data to write new data. If the read-modify-write operation fails, there is a risk that already written data may be lost. By not processing the write command from the host or user containing the size smaller than the error correction block size, the read-modify-write process is not necessary. Accordingly, even if an abnormal event such as a power failure occurs, there is no risk of losing already written data and a high reliability is retained.
(8) In an optical disc drive system with the data protection function for preventing user data rewrite, if any defect is detected during data read or write, management data in a defect management area of the optical disc is updated.
While data miss-erase or overwrite is prevented, the defective sector is subjected to the replacement process by using the rewrite function so that reliability can be improved without lowering the performance.
(9) An optical disc with a data protection function is provided which has a same physical format as a standard optical disc and a different range of address data assigned to a plurality of data recording unit areas from the standard optical disc, the standard optical disc having a plurality of unrewritable address data and the data recording unit areas identified by the address data and being freely rewritable.
With this optical disc, even if an optical disc with the data protection function is driven with a conventional optical disc drive system which cannot recognize the data protection function, the conventional optical disc drive system cannot access the target data write area because the target address does not exist at the position expected by the conventional optical disc drive system. There is therefore no risk that the conventional optical disc drive system without the data protection function may erroneously destroy data through erase or overwrite. A high reliability of the data protection function can therefore be improved. Further, the address data of a conventional optical disc is not overlapped with and is perfectly different from the address data of the optical disc with the data protection function. By utilizing this point, the conventional optical disc and the optical disc with the data protection function can be easily discriminated.